Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $107.57   9.468%   $117.7547   $117.75   $117.75   $117.80  
  Purchase #2 $135.67   6.352%   $144.2878   $144.29   $144.30   $144.30  
  Purchase #3 $186.29   7.336%   $199.9562   $199.96   $199.95   $200.00  
  Purchase #4 $185.87   9.316%   $203.1856   $203.19   $203.20   $203.20  
  Purchase #5 $205.64   8.139%   $222.377   $222.38   $222.40   $222.40  
  Purchase #6 $101.28   9.701%   $111.1052   $111.11   $111.10   $111.10  
  Purchase #7 $73.60   4.401%   $76.8391   $76.84   $76.85   $76.80  
  7 purchase totals = $995.92       $1,075.5056   $1,075.52   $1,075.55   $1,075.60